In this longitudinal study of the development of mastery motivation, the goals are to determine whether mastery motivation in infancy is predictive of later mastery behavior and to determine the role of early parent-infant interaction in the development of mastery behavior at 2 and a half years. The relationships between cognitive functions and mastery motivation during the preschool years is also being studied. An important part of this study has been the development of methods to assess similar aspects of mastery at 2 and a half years as were studied at 6 and 12 months of age. Data have been collected in a focused play session, an observation of the infant's free play with the mastery toys, observation of the childlren's mastery of learning problem, and a brief observation of mother-child interaction with another set of toys. Data on cognitive development have been obtained by the McCarthy scales. Preliminary analyses suggest that visual attenponents of mastery.